Controllable in situ generated carbon black hollow silica (C@h-SiO2) photonic crystal inks with highly saturated structural colors

The structural color of photonic crystals is usually whitish and has low saturation due to multiple incoherent scattering effects, limiting its application in practical visual observation. Herein, by controlling the calcination time of PS@SiO2 nanoparticles, we obtain hollow SiO2 with different in situ generated carbon black contents and assemble them into photonic crystal inks (PCIs). PCIs have excellent saturation and high crystallinity due to the in-situ generated carbon black capable of absorbing incoherently scattered light without affecting particle as-sembly. PCIs are further converted into non-close-packed photonic crystal films with highly saturated structural colors by photopolymerization of resins. This photonic crystal film can be swollen by an ethanol-water mixture, resulting in structural color changes and shifts in reflection peaks. Moreover, the photonic crystal film can dynamically change from a dry opaque state to an ethanol-wetted translucent state. Such solvent-responsive photonic crystal films with highly saturated structural colors are expected to be used in alcohol sensors and color anti-counterfeiting labels.

Automated summary

By controlling the calcination time, hollow SiO2 nanoparticles with different carbon black contents were obtained and assembled into photonic crystal inks (PCIs). The PCIs exhibited excellent saturation and high crystallinity, and were further converted into non-close-packed photonic crystal films. The films showed solvent-responsive structural color changes and shifts in reflection peaks, and could dynamically change from an opaque to a translucent state.